It is understood Blues star Ramires told team-mates that he heard the referee saying ‘shut up you monkey’ after a dispute with midfielder Jon Obi Mikel.

His claim was allegedly supported by his Brazilian team-mate David Luiz , who unlike Ramires, speaks good English.

At the time, both players were asked by club staff whether they were sure it was the word ‘monkey’ and not ‘Mikel’, which they heard Clattenburg say, to which both were positive.

Clattenburg denies making any such slur, and has the full backing of his assistants, who were all connected by headsets to the man from County Durham, and would have likely heard any insults.

Now, according to the Daily Mail, the Blues have employed a team of external lawyers to provide them with legal advice on whether their players’ evidence will stand up to the FA’s burden of proof.

A source also told The Sun: ‘There’s always a lot of noise on the pitch and the players could easily have misheard.’

Police have confirmed they have launched a formal investigation into complaints from the Society of Black Lawyers against Clattenburg, although the FA have been informed they do not need to halt their own proceedings.